Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$211.27	12.239%	$237.1273	$237.13	$237.15	$237.10
Purchase #2	$93.66	7.721%	$100.8915	$100.89	$100.90	$100.90
Purchase #3	$35.49	12.193%	$39.8173	$39.82	$39.80	$39.80
Purchase #4	$86.48	6.519%	$92.1176	$92.12	$92.10	$92.10
Purchase #5	$39.78	7.782%	$42.8757	$42.88	$42.90	$42.90
Purchase #6	$69.62	3.619%	$72.1395	$72.14	$72.15	$72.10
Purchase #7	$96.61	6.180%	$102.5805	$102.58	$102.60	$102.60
7 purchase totals =	$632.91		$687.5494	$687.56	$687.60	$687.50